president obama addressed the nation in hours after the bombing in boston briefly and says he has spoken with leaders and assured them the federal government will do everything in his power to help survivors and the president prom prised th the -- promised they will find those responsible. >> we do not know who did this or y people shouldn't jump to conclusions before we have the facts but we will get to the bottom this and find out who did this and why they did this. any response -- any responsible individuals, any responsible groups will feel the full weight of justice. >> that is just after 6:00 this evening, washington time, boston time. after the president spoke workers at the u.s. capitol lowered the flag there in memory of the innocent people who died today. doug mcelway is live in washington this tuesday morning what is the mood been there in hours after attacks? >> there are three components to it. washington is on alert z it's huge investigative capabilities ramping up. the president put think the way. >> i just want to reiterate we'll find out who did this and hold them accoun